/*
 * Copyright (C) 2012 ZXing authors
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.dtr.zxing.camera;

import android.annotation.SuppressLint;
import android.content.Context;
import android.hardware.Camera;
import android.os.AsyncTask;
import android.os.Build;
import android.util.Log;

import java.util.ArrayList;
import java.util.Collection;
import java.util.concurrent.RejectedExecutionException;

public class AutoFocusManager implements Camera.AutoFocusCallback {

	private static final String TAG = AutoFocusManager.class.getSimpleName();

	private static final long AUTO_FOCUS_INTERVAL_MS = 2000L;
	private static final Collection<String> FOCUS_MODES_CALLING_AF;

	static {
		FOCUS_MODES_CALLING_AF = new ArrayList<String>(2);
		FOCUS_MODES_CALLING_AF.add(Camera.Parameters.FOCUS_MODE_AUTO);
		FOCUS_MODES_CALLING_AF.add(Camera.Parameters.FOCUS_MODE_MACRO);
	}

	private boolean stopped;
	private boolean focusing;
	private final boolean useAutoFocus;
	private final Camera camera;
	private AsyncTask<?, ?, ?> outstandingTask;

	public AutoFocusManager(Context context, Camera camera) {
		this.camera = camera;
		String currentFocusMode = camera.getParameters().getFocusMode();
		useAutoFocus = FOCUS_MODES_CALLING_AF.contains(currentFocusMode);
		Log.i(TAG, "Current focus mode '" + currentFocusMode + "'; use auto focus? " + useAutoFocus);
		start();
	}

	@Override
	public synchronized void onAutoFocus(boolean success, Camera theCamera) {
		focusing = false;
		autoFocusAgainLater();
	}

	@SuppressLint("NewApi")
	private synchronized void autoFocusAgainLater() {
		if (!stopped && outstandingTask == null) {
			AutoFocusTask newTask = new AutoFocusTask();
			try {
				if (Build.VERSION.SDK_INT >= 11) {
					newTask.executeOnExecutor(AsyncTask.THREAD_POOL_EXECUTOR);
				} else {
					newTask.execute();
				}
				outstandingTask = newTask;
			} catch (RejectedExecutionException ree) {
				Log.w(TAG, "Could not request auto focus", ree);
			}
		}
	}

	public synchronized void start() {
		if (useAutoFocus) {
			outstandingTask = null;
			if (!stopped && !focusing) {
				try {
					camera.autoFocus(this);
					focusing = true;
				} catch (RuntimeException re) {
					// Have heard RuntimeException reported in Android 4.0.x+;
					// continue?
					Log.w(TAG, "Unexpected exception while focusing", re);
					// Try again later to keep cycle going
					autoFocusAgainLater();
				}
			}
		}
	}

	private synchronized void cancelOutstandingTask() {
		if (outstandingTask != null) {
			if (outstandingTask.getStatus() != AsyncTask.Status.FINISHED) {
				outstandingTask.cancel(true);
			}
			outstandingTask = null;
		}
	}

	public synchronized void stop() {
		stopped = true;
		if (useAutoFocus) {
			cancelOutstandingTask();
			// Doesn't hurt to call this even if not focusing
			try {
				camera.cancelAutoFocus();
			} catch (RuntimeException re) {
				// Have heard RuntimeException reported in Android 4.0.x+;
				// continue?
				Log.w(TAG, "Unexpected exception while cancelling focusing", re);
			}
		}
	}

	private final class AutoFocusTask extends AsyncTask<Object, Object, Object> {
		@Override
		protected Object doInBackground(Object... voids) {
			try {
				Thread.sleep(AUTO_FOCUS_INTERVAL_MS);
			} catch (InterruptedException e) {
				// continue
			}
			start();
			return null;
		}
	}

}
